Objetivou-se com este trabalho comparar histologicamente o desenvolvimento ontogen?tico de
duas esp?cies de peixes end?micos da bacia do rio S?o Francisco, Prochilodus argenteus
(curimat?-pacu) e Lophiosilurus alexandri (pacam?). As coletas para as an?lises histol?gicas
foram realizadas a cada 24 horas a partir do momento da eclos?o at? o 14? dia p?s-eclos?o
(DPE) para a observa??o do desenvolvimento larval e at? o 39? DPE para a observa??o do
desenvolvimento gonadal. As larvas foram fixadas inteiras em solu??o de Bouin e as l?minas
histol?gicas foram coradas pelo m?todo de Hematoxilina-Eosina. Larvas de pacam? exibiram
um tamanho corporal maior em rela??o ?s larvas de curimat?-pacu desde a eclos?o. Larvas de
pacam? apresentaram a abertura da boca e in?cio da pigmenta??o dos olhos no momento da
eclos?o, enquanto que nas larvas de curimat?-pacu, esses eventos foram observados no 1? DPE.
No curimat?-pacu a visualiza??o e a insufla??o da bexiga natat?ria ocorreram no 1? e 3? DPE,
respectivamente, sendo esses eventos mais tardios no pacam?, com visualiza??o no 2? e
insufla??o no 8? DPE. Os gr?nulos de vitelo foram absorvidos no 4? DPE pelo curimat?-pacu e
no 10? DPE pelo pacam?. No 7? DPE, o tubo digest?rio do pacam? apresentou-se mais
diferenciado em rela??o ao curimat?-pacu. O sistema digest?rio de ambas as esp?cies ao 14?
DPE demonstraram caracter?sticas relacionadas aos seus respectivos h?bitos alimentares, com
est?mago amplo e intestino curto no pacam?, t?picos de h?bito carn?voro; est?mago com fun??o
mec?nica e intestino longo no curimat?-pacu, t?picos de h?bito detrit?voro. O tecido epitelial de
revestimento, formado por uma ?nica camada de c?lulas nas larvas rec?m-eclodidas (0 DPE),
apresentou diferencia??o ao longo dos dias, exibindo presen?a de escamas no curimat?-pacu e
numerosas c?lulas ?club? na regi?o epitelial intermedi?ria do pacam?, em avalia??es realizadas
ao 39? DPE. Analisando os indiv?duos com 39 DPE, verificou-se a presen?a de g?nadas
indiferenciadas com c?lulas som?ticas e c?lulas germinativas primordiais que foram observadas
realizando migra??o no sentido caudo-cranial desde o 1? DPE em ambas as esp?cies. P?de-se
concluir que as altera??es anat?micas observadas durante a ontogenia de larvas P. argenteus e
L. alexandri est?o diretamente relacionadas ao h?bito alimentar e ao comportamento inerente ?
cada esp?cie, sendo uma detrit?vora que nada ativamente na coluna d??gua, e outra carn?vora
que habita regi?es de fundo, respectivamente. Aos 39 dias p?s-eclos?o, em ambas as esp?cies
n?o foram observados ind?cios histol?gicos de diferencia??o sexual.Banco do Nordeste do Brasil (BNB)Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq)Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES)Disserta??o (Mestrado) ? Programa de P?s-Gradua??o em Zootecnia, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2016.The objective of this work was to compare histologically the ontogenetic development of two
endemic species of fish from the S?o Francisco river basin, Prochilodus argenteus (curimat?-pacu)
and Lophiosilurus alexandri (pacam?). The samples for the histological analyzes were
performed every 24 hours since the moment of hatching until the 14th day post-hatching (DPH)
for observation of the larval development and until the 39th DPH for the observation of gonadal
development. The whole larvae were fixed in Bouin's solution and the histological slides were
stained by the Hematoxylin-Eosin method. Pacam? larvae exhibited a larger body size relative
than the curimat?-pacu larvae since hatching. Pacam? larvae presented the mouth opening and
pigmentation of eyes beginning at the time of hatching, whereas in curimat?-pacu larvae, these
events were observed in the 1st DPH. The visualization and the inflation of the swim bladder
in the curimat?-pacu, occurred in the 1st and 3rd DPH, respectively, being these events in the
pacam? later, with visualization in the 2nd and insufflation in the 8th DPH. The yolk granules
were absorbed in the 4th DPH by the curimat?-pacu and in the 10th DPE by the pacam?. In the
7th DPH, the pacam??s digestive tube was more differentiated than curimat?-pacu. The
digestive system of both species at the 14th DPH has features of it eating habits the pacam?,
with a broad stomach and a short intestine in the pacam?, typical of a carnivorous habit; stomach
with a mechanical function and a long intestine in curimat?-pacu, typical of detritivorous habit.
The epithelial lining tissue, formed by a single layer of cells in the newly hatched larvae (0
DPH), showed a differentiation throughout the days, exhibiting scales in curimat?-pacu and
numerous club cells in the middle epithelial region of the pacam?, at evaluations carried at the
39th DPH. Analyzing the individuals with 39 DPH, the presence of undifferentiated gonads
with somatic cells and primordial germinative cells were observed, which has a caudate-cranial
migration since 1st DPH in both species. It was concluded that the anatomical alterations of the
ontogeny of P. argenteus and L. alexandri larvae are directly associated to the feeding habit
and the inherent behavior of each species, being these detritivorous that nothing actively in the
column of water and carnivorous that inhabits bottom regions, respcectively. At the 39 day
post-hatching, both species hasn't evidenced of sexual differentiation